Foucault

/French fuko/

noun

1.

Jean Bernard Léon (ʒɑ̃ bɛrnar leɔ̃). 1819–68, French physicist. He determined the velocity of light and proved that light travels more slowly in water than in air (1850). He demonstrated by means of the pendulum named after him the rotation of the earth on its axis (1851) and invented the gyroscope (1852)

2.

Michel. 1926–84, French philosopher and historian of ideas. His publications include Histoire de la folie (1961) and Les Mots et les choses (1966)

(f-kō') French physicist who determined that light travels more slowly in water than in air, confirming predictions made by the wave theory of light. In 1850 Foucault also measured the absolute velocity of light. In 1851, by using a type of pendulum that is now named after him, Foucault demonstrated the rotation of the Earth, and in 1852 perfected a gyroscope for the same purpose.